This invention relates to an adjustable rotor and a radial piston machine or device which may utilize an adjustable rotor. The device utilizes either liquid or gaseous fluids or mixtures thereof such as, for example, in internal combustion and steam engines. The machine and rotor are usable as a fluid pump, fluid compressor, fluid motor or engine.
Generally, a radial piston device usable as a fluid pump, compressor, or motor or engine has the following elements: a circular or cylindrical casing with side or end walls and/or covers, a shaft with an eccentric journalled by bearings and extending through the central part of the casing and covers, and a cylinder block which may be combined in one piece with the casing. The cylinder block has a number of cylinders, each fitted with a piston and radially arranged in the cylinder block. During operation as a pump or compressor, rotation of the eccentric shaft drives the pistons to move reciprocatingly in the cylinders. Conversely, if operated as a motor or engine, the pistons impart rotational movement to the eccentric shaft. Contingent on design, the output of a radial piston device can be fixed or variable, and many machines have been developed based on the above mentioned principles.
Certain problems are common with many design configurations of current fluid pumps, compressors and motors and these problems are not necessarily confined to radial piston devices. Such problems are due primarily to heat, sound, and vibratory energy losses caused by the generation of mechanical and fluid friction. For example, in most positive displacement piston devices, friction induced wear or "galling" is common in the shoe area of a piston, as well as uneven cylinder wear due to lateral forces exerted on the lower areas of the cylinder walls. Many devices also contain off-loaded shafts and bearings, unbalanced mechanical and fluid dynamics, pressurized casings, fluid flow restrictions, or moveable masses such as stroke rings, blocks, or casings. These and other structural design deficiencies result in friction losses, increased wear, excessive sound, and reductions in performance, reliability or both while limiting the capability of the machine to endure high pressure surge peaks or achieve sustained higher operating pressures. Additionally, the rotational speed of such devices is also limited, primarily because of mechanical factors and fluid dynamics, and when rotational speed increases beyond the rated revolutions per minute (RPM), efficiency decreases significantly.
Failures of such equipment are often induced by contamination of the fluid medium or high pressure surge peaks caused by misuse, abuse, or improper design of the operating systems. Repair of such equipment usually requires skilled mechanics and special tools and causes costly downtime. Often, complete replacement of a unit is more cost effective than repair because prime components such as casings, blocks, cylinders, and shafts have undergone critical wear and, therefore, have become effectively unserviceable. Additionally, such equipment is often subjected to environmental extremes and operated outside of design or maintenance specifications, decisively increasing wear while diminishing the operating efficiency of the device. A device that would permit convenient on-site replacement of wear-prone parts, particularly while under operation, while also reducing wear on, and maintenance requirements for, prime components would be extremely beneficial, especially in applications where minimization of downtime is critical.
Generally, current fluid mechanical devices have narrow ranges of peak operating efficiency within their rated pressure, volume of flow, and RPM. Serious performance degradation occurs when a device is operated outside of its design parameters, and it is therefore common trade practice to size a fluid pump or similar device to a specific task. In an attempt to satisfy the infinite combination of system design possibilities, there are a multitude of such devices manufactured, with each device having unique size and shape characteristics. If the working pressure, flow rate, or RPM factors change over a wide range, the mean efficiency is dramatically reduced.
Equipment that improves the overall efficiency of fluid-handling or fluid-power systems would also offer substantial technology advancement opportunities. Although it is possible to identify many past improvements to the art of fluid mechanics, modern methods and processes are requiring durability, flexibility, and pressure capabilities that test the limits of existing technology. Also, many present-day pumps, compressors, motors and engines require specialized parts and processes to manufacture, and are therefore not necessarily conducive to mass production and standardization.
System efficiency improvements, particularly in fluid-power applications, are possible by constructing more durable machines capable of tolerating higher standard operating pressure. Higher norms of working pressure provide definite advantages by making it feasible to reduce the size and the weight of hydraulic actuators such as cylinders and motors. This is of particular significance for mobile, aviation, and aerospace hydraulic applications. However, the common mechanical and fluid dynamic problems of existing fluid machines are multiplied with increases in operating pressure. Durability improvements to fluid-power equipment allowing for increased pressure utilizations would effectively allow system design enhancements yielding significant weight reductions.
The limitations of today's fluid machines have also been defined by their individual narrow optimum working ranges and physical characteristics. Each device is intended for a specific application, and the specific internal design and external configuration impose severe limitations on flexibility of use within a system design. A fluid pump, compressor or motor that permits the use of modular interchangeable parts to supply the needs for a broad spectrum of operating requirements would be cost effective for manufacturer, vendor, and end-user.
In addition to modularity of parts, system efficiencies could be further enhanced by modularity of shape. Although some current machines couple units on the Same shaft, a long axis of drive normally requires modifications to the device itself or additional mounting or support means. The ability to couple individual units closely on one drive shaft without equipment modifications, excessive overall shaft length, and undue torsional shaft dynamics would exhibit a distinct advantage. These advantages are useful for pumps and compressors in powered devices and for combustion and other types of engines and fluid power motors in powering devices.
For instance, mobile heavy equipment industries commonly use a massive gear casing that houses complex gear trains for the purpose of providing multiple power take-off shafts to power the number of hydraulic pumps necessary for a single piece of equipment. Often, this component is a casing assembly designed for use in several lines or types of equipment, and in each specific application certain shafts and associated gears may go unused due to configuration and design mismatch, even though these gear trains consume energy in full-time operation and add to the cost of manufacturing the assembly. These large gear casings could be eliminated or down-sized by an improved ability to stack multiple units for separate fluid-power circuits on one primary drive shaft. Other examples of fluid-handling applications that would benefit from such improved stacking of units include fluid dispensing and fluid metering needs of the agricultural, petroleum/chemical, and food processing industries. Standby or extra functional units for safety, emergency, or other utilizations could also be more easily provided.
It has long been recognized that the ability to supply the exact pressure and volume of flow requirements for a system by controlling the output of a pump or compressor, independent of the input RPM while under operating load conditions, substantially reduces overall energy consumption and simplifies the system design. This capability is called continuously-variable dynamic control of the pumping source and improvements of this feature would substantially increase system efficiency.
Fixed output high-pressure or low-pressure pumps and compressors are very inefficient because they are usually sized to meet maximum load specifications and require sufficient RPM to provide a constant over-production of output. For example, normally the downstream actuators used in fluid-power systems do not require the maximum output that is generated, and subsequent control of excess output is commonly accomplished by additional downstream valves and components that divert excess volume and/or pressure to a reservoir, the unused output energy thus dissipating in the form of heat and often requiring supplemental cooling components.
Refrigeration and air-conditioning equipment and some hydraulic circuits, on the other hand, have a demand that is often satisfied by an intermittent fixed maximum output. In such cases control is usually accomplished by cycling, the on-again/off-again control of a fixed output compressor or pump by the use of a clutch mechanism, which is both inefficient and mechanically detrimental.
Traditional methodologies of achieving variable dynamic output control of a positive displacement source have taken exotic directions as exhibited by complicated vane, radial, and axial designs. Common fluid mechanics problems include the slow response of moveable masses such as stroke-rings or casings, sealing difficulties with pressurized casings, friction wear associated with off-loaded shafts and bearings, galling of piston shoe areas, and excessive sound. Current variable output, dynamically controlled pumping options are costly to manufacture and of questionable performance and durability, even when operated within their narrow design ranges, and particularly when dealing with high pressure applications. The adjustable rotor of the present invention provides solutions for such problems.
Simple powering devices such as combustion engines generally have fluctuating drive shaft RPM, and drive sources such as electric motors usually have more or less constant RPM but also often have continuously variable output requirements. In addition to the complex internal mechanical designs presently available to supply variable dynamic output control of the pumping source, other equally extensive supplementary electrical and mechanical systems have more recently been developed to externally control the input drive shaft RPM of a pump in an attempt to improve overall fluid mechanics system efficiency. In summary, these factors indicate the need to develop improved, simplified, and affordable variable dynamic control of fluid machines.